Many sport and utility vehicles are equipped with relatively large side-mounted rear view mirrors of a type which comprises a mirror housing mounted on a hollow "gooseneck" support arm. This term "gooseneck" is used because the arm is bent at a right angle to provide a first upright length which is secured to the vehicle bodyside by means of a mounting assembly and a second, normally outwardly extending length which is attached to the mirror housing or, more accurately, a structure within the housing. It is desirable to mount the gooseneck arm to the body side mount assembly in such a way as to permit the mirror assembly to be folded inwardly toward the vehicle bodyside, thus reducing the overall width of the vehicle where, for example, it is desired to pass the vehicle through an automatic carwash or to travel through a narrow passageway for other reasons which put side mounted mirrors at risk.
It is common in such an arrangement to provide a mechanical detent which assists the operator of the vehicle in finding the normal viewing position when returning the mirrors from the folded position. U.S. Pat. No. 5,028,029, issued Jul. 2, 1991 to Marlon E. Beck et al. illustrates one way of providing such a detent. In the Beck patent, the upright length of the gooseneck is provided with a longitudinally fluted or grooved terminal portion which cooperates with detent ribs on one or more plastic clamp members. The ribs fit into grooves on the arm to define the normal viewing position and to yieldably permit rotation of the gooseneck arm relative to the clamp when folding of the mirror is desired.
Another detent mechanism for vehicle rear view mirrors is illustrated in U.S. Pat. No. 4,477,199, issued Oct. 16, 1984 to Manzoni. Manzoni illustrates a mirror support arm having both detent grooves and protrusions which cooperate with bosses on a flange which resiliently contacts the mirror support during rotation thereof.
Both the Beck and Manzoni detents are relatively complex in design and appear to provide relatively soft detents. These structures also appear to provide only limited control over breakaway and rotation torques; i.e., the relatively high torque which is needed to bring the arm out of the detent and the relatively low but still significant torque which is required to produce continuing rotation of the arm relative to the bodyside clamp after the detent has been disengaged. It is, of course, desirable to produce an assembly in which these torque numbers are relatively predictable and stable over a range of manufacturing and assembly tolerances as well as operating temperatures.